The present invention relates generally to automotive HVAC systems for controlling the environment of an automobile passenger compartment. More particularly, the invention relates to a flow management system for controlling refrigerant flow in an automotive HVAC system.
This application is related to co-pending applications all filed on Nov. 12, 1998 sand titled Refrigerant Flow Management Center For Automobiles, Controller For Reversible Air Conditioning And Heat Pump HVAC System For Electric Vehicles, Anti-Fog Controller For Reversible Air Conditioning And Heat Pump HVAC System For Electric Vehicles, Controller For Heating In Reversible Air Conditioning And Heat Pump HVAC System For Electric Vehicles, Air Handling Controller For Hvac System For Electric Vehicles, and System For Cooling Electric Vehicle Batteries. Each of these applications is incorporated by reference into the present application.
Automotive climate control systems have traditionally been single loop designs in which the full volume of refrigerant flows through each component in the system. In operation, refrigerant in the vapor phase is pressurized by a compressor or pump. The pressurized refrigerant flows through a condenser which is typically configured as a long serpentine coil. As refrigerant flows through the condenser, heat energy stored in the refrigerant is radiated to the external environment resulting in the refrigerant transitioning to a liquid phase. The liquefied refrigerant flows from the condenser to an expansion valve located prior to an evaporator. As the liquid flows through the expansion valve it is converted from a high pressure, high temperature liquid to a low pressure, low temperature spray allowing it to absorb heat. The refrigerant flows through the evaporator absorbing heat from the air that is blown through the evaporator fins. When a sufficient amount of heat is absorbed the refrigerant transitions to the vapor phase. Any further heat that is absorbed raises the vaporized refrigerant into a superheated temperature range where the temperature of the refrigerant increases beyond the saturation temperature. The superheated refrigerant flows from the outlet of the evaporator to the compressor where the cycle repeats.
Generally, the refrigerant flowing into the compressor should be in the vapor phase to maximize pumping efficiency. The operation of the refrigerant loop in conventional automotive HVAC systems is controlled by cycling the compressor on and off as well as by varying the volume of refrigerant that is permitted to flow through the expansion valve. Increasing the volume of refrigerant that flows through the valve lengthens the distance traversed by the liquid before it changes to the vapor phase, allowing the heat exchanger to operate at maximum efficiency.
Advances in automotive HVAC systems have led to zone temperature control systems in which different zones of an automobile are independently controlled. Zone control systems generally include an evaporator and expansion valve for each zone. The refrigerant flows through a compressor and condenser, then is split by a system of valves before flowing to the expansion valve and evaporator of each zone. The refrigerant flowing out of the evaporator of each zone is then recombined before returning to the compressor. A complex series of valves and plumbing is generally required to maintain a balanced HVAC system that provides individualized control for each of the zones. The refrigerant plumbing associated with zone control systems is significantly more complex than the plumbing of prior single loop designs.
The complexity of refrigerant plumbing has further increased with the recent implementation of reversible heat pump systems in automobiles. In a reversible heat pump system the direction of the refrigerant flow is controlled by a four-way switch, thus permitting the HVAC system to operate in both a heating mode and a cooling mode. In the cooling mode refrigerant flows from the compressor through an outside coil (condenser) and into an expansion valve and inside coil (evaporator) before returning to the compressor. Heat energy is extracted from air that is blown through the inside coil (evaporator), thus providing cooled air to the passenger compartment. In the heating mode the four way valve reverses the flow of refrigerant through the coils, thereby reversing the function of the coils. Refrigerant flows from the compressor through the inside coil (condenser) then into an expansion valve and the outside coil (evaporator) before returning to the compressor. Heat energy in the liquefied refrigerant flowing through the inside coil is absorbed by air that is blown through the coil into the passenger compartment thus providing heated air. For the reversible system to operate, valves with associated plumbing must be provided to bypass one of the expansion valves during each mode. When zone control is added to a reversible heat pump system the complexity and cost of the HVAC further increases. In addition to excessive cost, the system becomes less reliable due to the increased number of valves, plumbing, and control software required for the system.
One object of the present invention is to decrease the complexity of automotive HVAC systems by employing a pressure reducing assembly in the system to reduce the number of valves required to implement a reversible heating and cooling HVAC system.
Another object of the present invention is to integrate a receiver/drier function into the pressure reducing assembly to provide a centralized assembly for supplying refrigerant to the system heat exchangers.
A further object of the present invention is to provide a pressure reducing assembly with outlets for providing liquid refrigerant to secondary heat exchangers that may be employed in automotive HVAC systems that implement multi-zone control.
It is now proposed, according to the present invention, to employ a centralized pressure reducing assembly to reduce the cost and improve the performance and reliability of automotive reversible HVAC systems by simplifying the interconnection of the HVAC components. Refrigerant lines from the system heat exchangers connect to bi-directional ports of a pressure reducing assembly which converts the high pressure refrigerant flowing from one heat exchanger into pressure reduced refrigerant that flows to the other heat exchanger. The pressure reducing assembly converts bi-directional refrigerant flow from the heat exchangers into unidirectional refrigerant flow through a pressure reducing device. Refrigerant emitted from the pressure reducing device flows out of the pressure reducing assembly to the other heat exchanger. The invention simplifies the interconnection of reversible HVAC systems by eliminating the complex plumbing and extra valves associated with conventional systems. In addition, the invention can further integrate the receiver/drier function into the pressure reducing assembly providing a centralized device for filtering refrigerant flow and ensuring a continuous supply of liquid refrigerant to the pressure reducing device. Also, the interconnection to secondary heat exchangers is simplified by routing high pressure liquid refrigerant from outlets in the receiver portion of the pressure reducing assembly.
The above described device is only an example. Devices in accordance with the present invention may be implemented in a variety of ways.